<!DOCTYPE html>
<html>
<head>
  <head>
    <style>
      table table
        { border-collapse: collapse; border-style: solid; border-width: 10px;
          border-color: green }
    </style>
  </head>
</head>
<body>
<table><tr>
  <td>
    <table>
      <tr><td></td></tr>
    </table>    
    <table>
      <tr><td></td></tr>
    </table>
  </td>
</tr></table>
</body>
</html>
